A New Insight into Growth Mechanism and Kinetics of Mesoporous Silica Nanoparticles by in Situ Small Angle X-ray Scattering.
A New Insight into Growth Mechanism and Kinetics of Mesoporous Silica Nanoparticles by in Situ Small Angle X-ray Scattering.
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DOI：
10.1021/acs.langmuir.5b01637
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发表时间：
2015-07
期刊：
影响因子：
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通讯作者：
Zhifeng Yi;L. Dumée;C. Garvey;Chunfang Feng;F. She;James E. Rookes;S. Mudie;D. Cahill;L. Kong
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文献类型：
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作者：
Zhifeng Yi;L. Dumée;C. Garvey;Chunfang Feng;F. She;James E. Rookes;S. Mudie;D. Cahill;L. Kong
首次采用同步辐射时间分辨小角X射线散射（SAXS）技术研究了介孔二氧化硅纳米粒子（MSNs）的生长机理和动力学。同步加速器SAXS提供了无与伦比的时间分辨率和检测纳米尺寸物体的结构变化的能力，这对于理解小MSN（~ 20 nm）的生长机制是有益的。采用Porod不变量对正硅酸乙酯（TEOS）在SiO2中形成MSN的转化率进行了定量计算，并通过计算散射不变量与反应时间的函数关系，研究了不同溶液pH和温度下的生长动力学。发现MSNs的生长在高温和高pH下加速，导致更高的二氧化硅形成速率。模拟SAXS数据的胶束，其中一个定义良好的静电相互作用是假设，确定的十六烷基三甲基溴化铵（CTAB）胶束的大小和形状之前和之后，加入TEOS。结果表明，TEOS在CTAB胶束中的增溶作用使胶束尺寸增大，胶束形状由椭圆形变为球形。提出了一种新的“胀缩”机制。该机制提供了新的见解理解MSN生长的功能介孔材料的形成表现出可控的形态。SAXS分析与CTAB胶束的结构和TEOS的化学反应有关。本研究为了解MSN的生长动力学和机制提供了重要信息。
The growth mechanism and kinetics of mesoporous silica nanoparticles (MSNs) were investigated for the first time by using a synchrotron time-resolved small-angle X-ray scattering (SAXS) analysis. The synchrotron SAXS offers unsurpassed time resolution and the ability to detect structural changes of nanometer sized objects, which are beneficial for the understanding of the growth mechanism of small MSNs (∼20 nm). The Porod invariant was used to quantify the conversion of tetraethyl orthosilicate (TEOS) in silica during MSN formation, and the growth kinetics were investigated at different solution pH and temperature through calculating the scattering invariant as a function of reaction time. The growth of MSNs was found to be accelerated at high temperature and high pH, resulting in a higher rate of silica formation. Modeling SAXS data of micelles, where a well-defined electrostatic interaction is assumed, determines the size and shape of hexadecyltrimethylammonium bromide (CTAB) micelles before and after the addition of TEOS. The results suggested that the micelle size increases and the micelle shape changes from ellipsoid to spherical, which might be attributed to the solubilization of TEOS in the hydrophobic core of CTAB micelles. A new "swelling-shrinking" mechanism is proposed. The mechanism provides new insights into understanding MSN growth for the formation of functional mesoporous materials exhibiting controlled morphologies. The SAXS analyses were correlated to the structure of CTAB micelles and chemical reaction of TEOS. This study has provided critical information to an understanding of the growth kinetics and mechanism of MSNs.